Spectroscopic properties and transition probabilities of SiC cation.

This study calculates the potential energy curves of 12 Λ-S and 27 Ω states, which belong to the first dissociation channel of SiC cation. The potential energy curves are computed with the complete active space self-consistent field method, which is followed by the valence internally multireference configuration interaction approach with the Davidson correction. The transition dipole moments are determined. Core-valence correlation and scalar relativistic correction, as well as extrapolation of the potential energies to the complete basis set limit are included. The spin-orbit coupling effect on the spectroscopic parameters and vibrational properties is evaluated. The vibrational band origins, Franck-Condon factors, and Einstein coefficients of spontaneous emissions are calculated. The rotationless radiative lifetimes of the vibrational levels are approximately 10 s long for the eΠ state. The partial radiative lifetimes of vibrational levels are approximately 10 s long for the 2Π and 2Σ states, 10 to 10 s long for the 2Σ state and the first well of the 1Π state, and very short for the second well of the 1Π state. Overall, the emissions are strong for the 2Σ-cΣ, 2Σ-XΣ, 2Π-XΣ transitions, and for the second well of the 1Π-1Σ transition. The spectral range of emissions is determined. In terms of the radiative lifetimes and transition probabilities obtained in this paper, some guidelines for detecting these states are proposed via spectroscopy. These results can be used to measure the emissions from the SiC cation, in particular, in interstellar clouds.